The present invention relates to a device for applying two-state logic testing signals to an input of a logic circuit. The invention more particularly applies to the testing of a logic circuit, whereof one output supplies signals, whose logic states are dependent on the logic states of control signals applied to one of their inputs by a control means. Without it being necessary to disconnect the control means from the logic circuit to which it is connected, it makes it possible to impose testing signals on the input of said logic circuit in such a way as to be able to check the resulting signals at the output, no matter what the logic state of the signals simultaneously supplied by the control means. The device is more particularly intended for use in the testing of logic circuits making it possible to initiate urgent actions in nuclear reactors, on the basis of logic signals supplied by control means constituted by transducers, whose outputs supply control signals of the "all or nothing" type, said control signals having in fact logic states 1 or 0.
The invention is also applicable to the automatic testing of a plurality of logic circuits, by test signals having two logic states applied to the inputs of said circuits, without it being necessary to disconnect these circuits from the control means applying logic signals to their inputs.
At present, no testing device is known, which makes it possible to apply logic testing signals to the input of a logic circuit controlled by a control means, without having to disconnect said means from the logic circuit. Generally, when it is necessary to test a logic circuit by applying test signals to one input thereof, in order to observe at the output the corresponding resultant signals the control means is disconnected from the logic circuit, in such a way that the control signals do not disturb the test signals and conversely the test signals do not disturb the operation of the control means. The main disadvantage of disconnecting the control means from the logic circuit is that there is a doubt regarding the transmission of the control signals to the logic circuit when, with the test completed, the control means is again connected to the logic circuit. Thus, during said connection and after a test, faulty contacts may occur in the connection of the output of the control means to the input of the logic circuit.